The overall objective of the proposed studies is an understanding of the functional control of estrogen action in the anterior pituitary and hypothalamus, leading toward an explanation of the steroidal regulation of gonadotropin secretion and possibly uncovering novel methods or sites of action for modification of the process of ovulation. The general approach will be examination of qualitative and quantitative changes in estrogen receptors inducible by a variety of conditions and substances. The unique feature of the proposed studies is that the primary emphasis will be placed upon direct modification of estrogen-receptor interactions, either by alterations in the amount of functionality of the receptor molecules; this is significantly distinct from most studies of steroid hormone action which focus upon equilibrium, rather than kinetic, parameters of receptor dynamics. The experimental designs to be described herein are of such a nature as to allow detection of both positive and negative influences upon receptor populations, as well as tissue-specific responses to stimuli which can be regulated by the investigator. Therefore, the findings should find clinical relevance to situations involving impairment of normal ovarian function, and to the critical issue of contraceptive population control. BIBLIOGRAPHIC REFERENCES: Korach, K.S., and T. G. Muldoon, Inhibition of Anterior Pituitary Estrogen-Receptor Complex Formation by Low-Affinity Interaction with 5a-Dihydrotestosterone. Endocrinology 97:231, 1975. Greeley, G.H., Jr., T. G. Muldoon, and V.B. Mahesh, Correlative Aspects of Luteinizing Hormone-Releasing Hormone Sensitivity and Cytoplasmic Estrogen Receptor Concentration in the Anterior Pituitary and Hypothalamus of the Cycling Rat. Biol. Reprod. 13:505, 1975.